This invention relates generally to magnetic disk data storage systems, and more particularly to magnetic write transducers and methods for making same.
Magnetic disk drives are used to store an retrieve data for digital electronic apparatus such as computers. In FIGS. 1A and 1B, a magnetic disk data storage system 10 of the prior art is illustrated which includes a sealed enclosure 12, a disk drive motor 14, a magnetic disk 16, supported for rotation by a drive spindle S1 of motor 14, an actuator 18 and an arm 20 attached to an actuator spindle S2 of actuator 18. A suspension 22 is coupled at one end to the arm 20 and at its other end to a read/write head or transducer 24. The transducer 24 (which will be described in greater detail with reference to FIG. 2A) typically includes an inductive write element with a sensor read element As the motor 14 rotates the magnetic disk 16, is indicated by the arrow R, an air bearing is formed under the transducer 24 causing it to lift slightly off the surface of the magnetic disk 16, or, as it is termed in the art, to xe2x80x9cflyxe2x80x9d above the magnetic disk 16. Alternatively, see transducers, known as xe2x80x9ccontact heads,xe2x80x9d ride on the disk surface. Various magnetic xe2x80x9ctracksxe2x80x9d of information can be written to and/or read from the magnetic disk 16 as the actuator 18 causes the transducer 24 to pivot in a short arc as indicated by the arrows P. The design and manufacture of magnetic disk data storage systems is well known to those skilled in the art.
FIG. 2A depicts a magnetic read/write head 24 including a substrate 25 above which a read element 26 and a write element 28 are disposed. Edges of the read element 26 and write element 28 also define an air bearing surface ABS, in a plane 29, which can be aligned to face the surface of a magnetic disk 16 (see FIGS. 1A and 1B). The read element 26 includes a first shield 30, an intermediate layer 32, which functions as a second shield, and a read sensor 34 that is located within a dielectric medium 35 between the first shield 30 and the second shield 32. The most common type of read sensor 34 used in the read/write head 24 is the magnetoresistive (AMR or GMR) sensor which is used to detect magnetic field signals from the magnetic medium through changing resistance in the read sensor.
The write element 28 is typically an inductive write element which includes the intermediate layer 32, which functions as a first pole, and a second pole 38 disposed above the first pole 32. The first pole 32 and the second pole 38 are attached to each other by a back-gap portion 40, with these three elements collectively forming a yoke 41. The combination of a first pole tip portion 43 and a second pole tip portion 45 near the ADS are sometimes referred to as the yoke tip portion 46. A write gap 36 is formed between the first and second poles 32, 38 in the yoke tip portion 46. The write gap 36 is filled with a non-magnetic electrically insulating material that forms a write gap material layer 37. This non-magnetic material can be either integral with (as is shown here) or separate from a first insulation layer 47 that lies below the second pole 38 and extends from the yoke tip portion 46 to the back-gap portion 40.
Also included in write element 28 is a conductive coil 48, formed of multiple winds 49 which each have a wind height Hw. The coil 48 can be characterized by a dimension sometimes referred to as the wind pitch P, which is the distance from one coil wind front edge to the next coil wind front edge, as shown in FIG. 2A. As is shown, the wind pitch P is defined by the sum of the wind thickness Tw and the separation between adjacent winds Sw. The conductive coil 48 is positioned within a coil insulation layer 50 that lies above the first insulation layer 47. The first insulation layer 47 thereby electrically insulates the coil layer from the first pole 32, while the coil insulation layer 50 electrically insulates the winds 49 from each other and from the second pole 38.
The configuration of the conductive coil 48 can be better understood with reference to a plan view of the read/write head 24 shown in FIG. 2B taken along line 2Bxe2x80x942B of FIG. 2A. Because the conductive coil extends beyond the first and second poles, insulation may be needed beneath, as well as above, the conductive coil to electrically insulate the conductive coil from other structures. For example, as shown in FIG. 2C, a view taken along line 2Cxe2x80x942C of FIG. 2A, a buildup insulation layer 52 can be formed adjacent to the first pole, and under the conductive coil layer 48. As is well known to those skilled in the art, these elements operate to magnetically write data on a magnetic medium such as a magnetic disk 16 (see FIGS. 1A and 1B).
More specifically, an inductive write head such as that shown in FIGS. 2A-2C operates by passing a writing current through the conductive coil layer 48. Because of the magnetic properties of the yoke 41, a magnetic flux is induced in the first and second poles 32, 38 by write currents passed through the coil layer 48. The write gap 36 allows the magnetic flux to fringe out from the yoke 41 (thus forming a fringing gap field) and to cross a magnetic recording medium that is placed near the ABS. A critical parameter of a magnetic write element is the flux rise time. As will be appreciated by those skilled in the art, a reduction of flux rise time allows for increased recording speed. It has been found that a reduced flux rise time can be achieved by shortening the yoke length YL as referred to in FIG. 2D. Thus, to obtain faster recording speeds, and therefore higher data transfer rates, it may be desirable to have a shorter yoke length YL. This relationship can be seen in the graph of yoke length YL versus flux rise time shown in FIG. 2D.
Another parameter of the write element is the number of winds 49 in the coil layer 48, which determines magnetic motive for (MMF) of a write element. With increasing number of winds 49 between the fly and second poles 32, 38, the fringing field is stronger and, thus, the write performance increases. However the number of winds is limited by the yoke length YL, shown in FIG. 2A, and the pitch P between adjacent winds 49. Therefore, to maximize the number of coil winds while maintaining fast write speeds, it is desirable to minimize the pitch P in design of write elements. The minimum pitch is, however, limited by practical considerations such as manufacturing, and cost.
One method which has been used to increase the number of winds while maintaining a small yoke length has been to use multiple coils stacked one on top of another. However, prior art multiple coil write heads have required the use of a center tap to interconnect the coils, leading to increased manufacturing cost and increased stack height. Thus there remains a need for a write head which can provide a relatively large number of windings in a yoke having a short yoke length and without use of a center tap. Such a device would preferably be relatively inexpensive to construct and have a small stack height.
The present invention provides a magnetic write element and method for making the same that delivers a high magnetic motive force while also providing a short flux rise time. The invention accomplishes this by using multiple coils stacked one on top of the other including the use of a bifilar coil. The multiple coils are interconnected without using a center tap by connecting the coils through vias which traverse no more than one layer of insulation at a time. In other words each coil is connected only to a coil which is adjacent to it. Thus, saving significant manufacturing cost as well as minimizing the stack height of the write head.
The write head is constructed as a combination read/write head built upon a ceramic substrate. The write element of the read/write head includes a first pole constructed of a magnetic material. A first insulating material is deposited on the first pole and a first coil having inner and outer contacts is plated onto the first insulating layer. A write gap material is provided on top of the first coil including a via through which electrical contact can be made with the first coil. A second and third coil are then formed on top of the write gap material each having an inner and an outer contact, and formed as a single bifilar coil. The inner contact of the second coil makes electrical connection with the inner contact of the first coil through the via in the write gap material.
A second insulation layer is provided on top of the second and third coils and, like the first insulation layer is provided with vias through which electrical contact can be made. A fourth coil having an inner and an outer contact is provided on top of the second insulation layer. The outer contact of the fourth coil makes electrical connection with the outer contact of the second coil through one of the vias formed in the second insulation layer, and the inner contact of the fourth coil makes electrical connection with the inner connection of the third coil.
A third insulation layer is then provided on top of the fourth coil over which is formed a second pole. The second pole connects magnetically with the first pole at a back gap portion. An electrical signal can be supplied to the coil assembly through the outer contact of the first coil and the outer contact of the third coil. It will be appreciated by those skilled in the art that the described write element provides a multiple coil assembly without the need for a center tap and while only connecting coils which are adjacent with one another, thereby providing a write element having a short yoke length, high magnetic motive force and relatively short stack height. Furthermore, these improvements are realized in a device which is relatively inexpensive to manufacture.
These and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following descriptions of the invention and a study of the several figures of the drawings.